The invention concerns a self-contained water system of the type commonly used in recreational vehicles and the like, and more particularly a system for controlling the internal flushing and cleaning of the waste fluid holding tanks of such a system.
Although the invention has other applications it will be assumed for convenience in the following discussion that it is installed in a recreational vehicle--a wheeled vehicle including living quarters and washing and toilet facilities and typically including two holding tanks for collecting waste fluids--a sewage tank for sewage and a so-called grey water tank for the remainder.
In conventional systems that holding tanks are connected to and drained through a tee connection accessible from outside the vehicle. A large flexible hose is connected to the tee outlet and carries the liquid waste to a receiving tank, typically underground and as provided at recreational camping grounds. Valves in the respective drain lines upstream of the tee permit selective draining of the tanks.
Holding tanks must be flushed and cleaned occasionally to maintain them and to minimize the accumulation of solids and sludge, especially in the sewage tank, and also to control odors. The volume and flow rate from the vehicle's own clean water supply storage tank is insufficient to flush these holding tanks adequately and, commonly, a garden hose is dragged into the interior of the vehicle and inserted in toilet or sink drains in an attempt to apply sufficient pressure and volume to flush and clean the holding tanks. At the same time, disinfectant or cleaning fluids may be added. But this method is at best inconvenient and easily results in damage and soiling inside the vehicle. In addition it is generally not possible to direct the flow of water from the hose onto all internal surfaces of the holding tanks so as to do an efficient cleaning and flushing job. Use of a team of two people, one inside the vehicle and one outside to control water flow and to manipulate the drain valves, reduces the risk of spillage and error but still leaves the system inefficient.
In an improved method, an auxiliary fluid line system feeds both tanks selectively from a common external inlet. This provides more convenient and effective flushing and cleaning.
It is of course necessary to avoid contamination of the pressurised water supply used for cleaning, by contact with effluent from the holding tanks during the flushing operation. Contamination might arise for example, from backflow from the flushing operation into the water supply. Or it may result from spilling in the "service area" when hoses are disconnected and siphoning may occur. If the supply system is communal or public, industry self-regulation or government regulation may require that the flushing system include particular safeguards or meet certain standards that reduce to an acceptable minimum the possibility of contamination. In some cases, the cost of required backflow prevention components may so increase the price of the optional tank flushing system as to severely limit its market.